


Family Roles

by SoloShikigami



Category: Undertale (Video Game)
Genre: Incest, Light Bondage, M/M, Underswap Papyrus (Undertale), Underswap Sans (Undertale)
Language: English
Status: Completed
Published: 2020-04-24
Updated: 2020-04-24
Packaged: 2021-03-01 20:40:14
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,912
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23823211
Author URL: https://archiveofourown.org/users/SoloShikigami/pseuds/SoloShikigami
Summary: Big brother Papyrus always looks out for the best interests of little brother Sans, even if it means disciplining him, but sometime big brothers need to be taught a lesson as well.
Relationships: Papyrus/Sans (Undertale)
Kudos: 42





	Family Roles

“S-s-sans, wh-what are you doing?” Papyrus stammered, sitting up straighter than he ever had in his life when he felt gloved fingers play along the notches of his spine.

“I’m just appreciating a beautiful work of art,” Sans murmured just loud enough for Papyrus to hear. “I don’t know if anyone tells you how lovely your spine is, Pappy.”

Papyrus grit his teeth, refusing to cry out when Sans mouthed at the bone, a barely-formed tongue darting between the ridges, lapping at sensitive cartilage.

The little skeleton had snuck up behind him and nestled his way under his oversized hoodie. It was beyond sneaky; no one would see Sans unless they went around the back of Papyrus’ station, and there was no reason for anyone to do so, and he knew it.

“Sans,” Papyrus murmured, trying to put as much warning into his voice as he could. “You know that’s not how brothers are supposed to behave.”

“Mmm, maybe, but also I’m sure that my big brother isn’t supposed to kiss me so lewdly while I’m trying to make breakfast, as you did this morning. The tacos nearly burned, and you know how I feel about wasted food.”

Papyrus went to retort, but it was cut off by those gloved fingers returning and playing along the other side of his spine, just beneath his ribcage.

“Also, what kind of older brother fucks his pleading baby brother against the bedroom door?”

Papyrus let out a quiet and very shaky whine as one hand fingered at his ribs and the other trailed lower down his spine.

“You keep playing that card, Pappy, and you keep underestimating me,” Blue said innocently. “I’m already sinfully aroused by the thought of what you’re going to do to me tonight for this little… indiscretion.”

“Sans,” Papyrus ground out between clenched teeth.

“Maybe you’ll shove your thick cock down my throat? You know how much I love the taste of you on my tongue. Or maybe you’ll demand I make my little pussy for you to pound, tell me what a good little brother I am to listen so well as I squirt all over your dick?”

As Sans spoke, he continued to worship Papyrus’ spine with soft touches and a nip of teeth. The tall skeleton was shaking with barely contained arousal by the time Sans pulled away.

“I’ll see you tonight, then, big brother?” Sans said brightly with a wink before he turned to skip away to his patrol.

“I don’t think so,” Papyrus growled, suddenly appearing in front of Sans and dropping a heavy hand on his shoulder. “You’re coming with me, you conniving little shit.”

“But Pappy!” Sans protested.

“But nothing!” he gripped Sans’ shoulder tightly and loomed over the little skeleton. “Your big brother needs to teach you a lesson.”

With a small _pop!_ the two skeletons disappeared.

~ * ~ * ~ * ~ * ~ * ~ * ~ * ~ * ~ * ~

Sans felt loving warmth blossom in his soul, knowing Papyrus kept a firm grip on him; he could never seem to get the hang of teleporting and he was always unsteady for a few moments, and the fact that Papyrus remembered that and held him until he was sure he was steady again always made Sans fall in love with him just a bit more.

While the loving hold was there, it was coupled with being immediately groped between his legs and a hand slipping up under his armor and a mouth latched onto his neck, suckling and nibbling with a possessive growl. Sans felt himself being moved, then the front of his body was pressed against something rounded, firm, but with some cushion. Once his vision righed itself again, he found he was being pinned against the arm of their couch.

“You are such a naughty little brother, Sansy,” Papyrus growled against his temple, thrusting the bulge forming in his crotch against Sans’ backside. “You thought you would get me all hot and bothered at my station and just leave me there? You would have spent your whole day all smug knowing that I’d be sitting there, squirming on that wooden stool with no way of relieving myself, knowing that I wouldn’t dare touch myself out in the open like that. Someone could have been watching us, too.”

“I figured it would keep you from boondoggling, and napping,” Sans explained with a small moan, reaching up to untie his cool handkerchief from his neck, giving his brother easier access to the sensitive bones there.

Papyrus bit down firmly on the newly exposed bone, relishing in the small cry of pain, and the following pleased whine. He hummed in satisfaction, kissing the bite, his soul thrumming in the fact that his baby brother would be sporting his mark under his scarf for at least a week.

“That was for talking back,” Papyrus murmured, continuing to run his hands all over Sans’ body. “It’s only because I love you so damn much; I love the way you squirm under my touches, I adore the sounds you make,” he wrapped one hand firmly around the front of his neck, “but you still have been a very, very naughty little brother.”

Sans, still gripping the beloved piece of bright blue fabric in one hand, put his hands over Papyrus’, guiding them to his chest and holding them close to his ribcage.

“Mmm, you started it,” Sans reminded him, pressing his hips back into the taller skeleton. “Maybe it is you who should be punished.”

“Oh, no, I don’t think so,” Papyrus said with a dark chuckle, sliding one hand up to press his fingers into Sans’ mouth. “As the elder brother, it is my job to make sure you are doing the right thing and punish you when you are not.”

Papyrus ground into Sans, pressing him harder into the arm of the couch, dragging a small, needy whimper from him. Papyrus took his fingers out of Sans’s mouth, now covered in his blue magic, and drew a line across his jaw and down his neck.

“So, Sansy, what do you have to say for yourself?” 

The body underneath him went still, then straightened, and Papyrus barely registered the slide of fabric across his wrist as he was struck dumb by the words preceding it.

“But sometimes, Papyrus, even the elder brother needs to be disciplined.”

The world turned upside down for a moment, Papyrus caught a brief look at his brother’s smirking face before he landed on his back on the couch. He felt a tug at his wrists, which were now bound and stretched over and behind his head.

“Mweh, heh, heh! I always tell you, big brother,” Sans said, gloved fingers trailing over the blue handkerchief that now bound Papyrus’ wrists together, down his arm, over the soft cotton of his hoodie and down his side as he sauntered over and then straddled him, pinning his legs down as well. “Never underestimate the Magnificent Sans!”

Papyrus opened his mouth, but no words came out, still in shock over the literal flip in their roles, and Sans took up the opportunity to capture his mouth, kissing him deeply. Sans only let up when it seemed Papyrus’ mind fully caught up to his new position and he began to squirm under him.

“Do you have something to say, Pappy?” Sans said innocently after breaking the kiss.

“Did you really just throw me onto the couch?” he asked.

“Yup! Mweh heh heh! I told you to not underestimate me!” Sans sat up and crossed his arms, tilting his head in a confident manner. “I have been training very hard, after all!”

Papyrus stared, really taking in what sort of strength Sans had to build to pull off this stunt. Since skeletons didn’t have muscles, it was a little difficult to gauge physical strength, but now his mind was going haywire imagining Sans forming his body with his magic and what sort of muscles would all but naturally show up in thanks to his hard work. He was brought back to reality when a rocking against his crotch caught his full attention, making him moan.

“Mmm, I can tell that you were thinking lewd things about me again,” Sans murmured, continuing to gently grind his hips against Papyrus’, his bright blue eyes shaping into hearts as his desire grew. “So naughty, Pappy, and you’re supposed to be setting the example for me? Tsk, tsk. Well, if lewd is what you want,” he leaned forward, grinding his entire body against him before whispering against his mouth, “then lewd is what you’ll get.”

Sans moved down Papyrus’ body, ignoring the way he hitched his hips up into him as he went.

“Oh, my, Pappy, what do we have here?”

Sans pushed Papyrus’ legs aside, so he could settle between them. Papyrus whimpered as Sans pressed his hand much, much too gently against the very prominent mound in his shorts, the glowing becoming evident even behind the fairly thick fabric. Sans giggled, pushing the hem of Papyrus’ hoodie up, one hand rubbing his spine to keep his lower half under his control as he continued to press and prod with his other hand, drawing hitched breaths and small gasps.

Papyrus was trying to keep his cool, but Sans was making it impossible; the soft, worn leather of his glove against his spine felt amazing, the teasing touches between his legs was driving him to madness. He knew his brother, and he knew Sans would want him to ask him nicely to relieve some of this tension.

And Papyrus really did not want to give him the satisfaction.

“How are you doing there, big brother?” Sans asked, leaning over to drag his tongue along his spine, making Papyrus arch into him. “I can continue punishing you, or you can apologize for riling me up this morning.”

Papyrus couldn’t help the stubborn glare he shot at Sans. Sans matched it then moved himself slightly lower so instead of licking his spine, he began to mouth at his clothed erection.

_You little bastard,_ Papyrus thought to himself. Sans enjoyed sucking him off, and Papyrus enjoyed it just as much.

Sans smiled, he knew that he could get what he wanted, but he had to push Papyrus just a little further. He unbuttoned his shorts, glancing up at him as he did so. Papyrus didn’t seem to waver, so he continued, gripping the zipper with his teeth to slowly pull it down.

Papyrus began to tremble slightly.

Sans continued, nuzzling in the opening of his shorts, breathing in the scent of his magic, holding back a giggle as he felt Papyrus squirm more and trying to hold back small whimpers. He glanced up, making sure he caught Papyrus’ eye when he reached out with his tongue and licked the spot right above the base his cock.

“Shit, Sans, please,” Papyrus babbled, unable to keep his breaking voice back.

“What is it, big brother?” Sans asked.

“Just… just…”

“You know what I want to hear.”

Papyrus made a sound between a defying growl and a pleading moan, but Sans remained steady, continuing to lap at his magic and rub his spine. Papyrus was stubborn, but so was Sans.

However, Papyrus was also impatient.

“All right, all right, fuck, Sans, I’m sorry, please, now can you just…”

“Mmm, I don’t know, Pappy,” Sans sat up, giving Papyrus a stern look and gripping his spine firmly. “How do I know you mean it, hmm? You have to convince me.”

“Sans, please,” Papyrus arched, trying to get any contact he could, but Sans’ hold was firm. “I’m sorry, Sans, I am so, so sorry, I promise I won’t do it again!”

“Heehee, well, you can do it, just don’t be so mean when the tables get turned,” Sans said brightly. “All right, the Magnificent Sans forgives you, big brother,” his voice dropped down as his grin turned from bright to mischievous. “Now, I would like to claim my prize, if that is all right with you?”

Papyrus nodded with a small whimper, and with a small chuckle, Sans pulled Papyrus’ shorts down a little more, just enough to free his hard cock. Papyrus shivered as Sans licked his teeth before bending to take him in one go. He still had a grip on his spine, which was good, otherwise he would have thrust hard into his mouth. Sans kept control, pulling off his cock slowly, scraping his teeth lightly along his shaft, before swallowing him down again.

“Stars, your mouth feels so fucking good,” Papyrus moaned. “You’re so good, knowing just what to do.”

Sans smiled around him, swirling his tongue around the head to gather beading magic before going down on him again.

It didn’t take long to whip Papyrus up into a frenzy of high-pitched moans and small pleas. Sans brought him to the edge of his peak, and then squeezed the base of his cock firmly, drawing an almost pained cry from him as he thrashed in protest.

“Now, now, Papyrus, take it easy or I will have to punish you again,” Sans said in a scolding tone, leaning over to kiss him. “Besides, you’re not the only one who’s horny.”

Papyrus blushed slightly; it was odd to hear such things from Sans, even in the throes of passion.

Sans got up and quickly undressed, though he made a small show of shimmying out of his pants. Papyrus stared at Sans’ body, which formed from the end of his ribcage and down; he was right in thinking that his magic would form the definition of muscle, and it was most definitely evident that Sans had been training hard. He posed for a moment, drinking in the attention, before he moved to straddle Papyrus again, palming his own hardening cock.

Papyrus couldn’t think of words, and instead watched as Sans gripped the thick orange rod of magic, pumping it a few times, before positioning himself and slowly lowering onto it.

“Ooohhh, Pappy,” Sans moaned. “This feels so good.”

Papyrus fought to not thrust - Sans would likely punish him for it - and instead tried to control his breathing. He wanted to shut his eyes to give him more of a fighting chance, but Sans had to lean forward and grip his jaw firmly.

“I want you to watch me, big brother,” Sans said.

Papyrus shuddered, whimpering as Sans lifted himself and then crying out when he lowered himself again.

“Yes, Pappy, let me hear you,” Sans murmured, his head leaning back as he drank in the begging undertone in his brother’s voice.

Papyrus whimpered and writhed under Sans as he slowly rode him, wishing he could free his hands, wishing he could touch his sweet little brother, wishing that he wasn’t so damn good at tormenting him like this.

“How do you like this, big brother?” Sans asked as he began touching his own chest, fingertips tracing across the ridges in the abdomen he formed and his rib cage. “You like me riding you? Watching your cock disappear inside of me? You feel so good, filling me, your cock twitching against my tight walls, I could do this all day, keep you nice and hard for hours, you could be my little toy an-!”

“Stars, Sans, please,” Papyrus finally broke. “Please, I can’t take this anymore, I want to cum so badly.”

“Do you?” Sans asked, sliding down and staying, squeezing himself around Papyrus to draw out a cry. “To be honest, I do, too. A bit of a shame, though, this does feel nice.”

Sans grinned and wiggled his bottom, enjoying the resulting moan.

“You’re evil,” Papyrus croaked.

“You say that only because I have the upper hand, but, I believe you’ve had enough,” Sans leaned forward, putting his hands on Papyrus’ chest. “Give me all you got, Pappy.”

Sans began to ride him fast and hard. Papyrus didn’t care to keep control of his voice, reaching his peak quickly. He arched up, nearly screaming as he finally found release, Sans moaning at the sensation.

“Good boy, Pappy, so good,” Sans murmured, rocking his hips again and milking Papyrus until he could feel his magic soften.

Papyrus had dropped back into the couch, body limp, bones trembling with the exertion. His bones tingled with magic, they were sensitive, which was why he gasped a little when Sans’ fingers ran down his legs.

“I’m proud of you, big brother, you did very, very well,” Sans praised, leaning forward to kiss him. “Surely, you could hang in there for a little while longer, though?”

Papyrus blinked in a daze. “W-what do you mean, Sans?”

“Mweh, heh, well, I need my turn after all.”

Papyrus was suddenly made aware that Sans was still sporting a hard-on as he ground his hips against him. Sans slipped back along his legs, moving them aside again to settle between them, fingers brushing along his pelvis, stirring his magic once more. Before he could voice a protest, Sans pressed an insistent finger into his entrance, awakening his desire once more.

“Are you ready for me, Pappy?” Sans asked, gently removing his finger and rubbing the head of his cock around the twitching magic, but not breaching him until he knew he had permission.

“Fuck, please, take me, Sans,” Papyrus begged.

“Language, big brother,” Sans chided gently, before he thrust into him.

Before Papyrus gave into his baby brother, he made a mental note that maybe letting him take control now and then wasn’t a bad thing.

**Author's Note:**

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